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EMF Compare/2012EMFCompareEnhancements


This work is developed by Obeo and sponsored by Ericsson in the context of the Polarsys.
It provides improvements for UML compare and merge with EGit and Papyrus both in term of features and in term of performances.
These features will be integrated in Juno, and the performance tests will be done before Juno SR1.

EMF Compare integration

Diff model restructuring to ease exploitation

The diff model provided as a result by EMF Compare can be quite complex to leverage for several reasons :

  • The model is missing an “origin” information (remote, local, ancestor, hierarchy, with user name when possible), leading to excessive abstract types of changes in the diff model.
  • “DiffGroup” have to be created/deleted on demand by the adopter modifying a diff model, this concept should be either deleted or have utility methods to make sure the diff model is valid.
  • Lack of browsing and cross-referencing APIs
  • DiffElements should be easily serializable for storage of DiffElement selections and reuse of these selections in order to open the comparison editors at the right place.

We are working on a new API to directly retrieve the following serializable information from each Diff:

    • Description as provided by Structural differences in the Eclipse compare
    • Modification type
    • Element Details e.g. class name, package name, diagram, etc.
    • Meta-Meta model details e.g. Eclass, EPackage
    • Model Location e.g. xmi-id
    • Diagram Details e.g. element name, type, etc..
    • Stereotype
    • Any other data needed to re-create a Model / Diagram diff

These API will specifically focus on making easier to reuse and integrate the diff model results in other tools like R4E.
It will be possible to re-create a Diff instance from the serialized information above.
UML and SysML comparison features will be updated accordingly.

EMF Compare usability

DiffElement selection

From a stored/serialized DiffElement, this feature enables the selection of the related DiffElement in the current comparison editor. If no DiffElement matches, open a new comparison editor which contains the DiffElement to select.

Contextual menu contribution

This feature enables to contribute your own right-click menu on the comparison editor, through extension point.

Undo/Redo support for the comparison editor

There is currently no way to undo merge operations done through EMF Compare. Support for undo/redo actions on these operations will be handled directly from the UI, with an accessible API for standalone use.

Conflict resolution wizard

Currently, conflicts detected by EMF Compare are resolved by overriding : users either select the "local" version or the "remote" version. A new wizard, accessible from the UI, will be added to help conflict resolution by merging some parts of the change.

Standalone comparison editor

Implementation of a standalone comparison editor that can be reused by third-party plugins to display comparison results.
The current comparison editor relies on the comparison editor framework provided by the Eclipse platform. It provides the advantage of a good integration in the Eclipse platform, but can be not enough customizable in some cases.
This feature includes both an editor mimicking the looks and behavior of the "standard" comparison editor, and the API to use and customize it out of the context of the team API.

UML Compare / Merge Performance Enhancements

After the work done in 2011, there are still some needs for enhancements to be able to support large model comparisons and to fully support logical models. These enhancements focus on restricting the scope of a comparison, and on getting faster and using less memory when we compare and merge large models.

Scoped models comparison

EMF Compare has the concept of a “scoped” comparison to ignore changes which are not in scope, but in term of implementation the complete UML model gets loaded (two or three versions of it depending on whether we need to detect conflicts or not).
Thanks to the Logical Model implementation we now have the ability to create the complete graph of files composing a model and their SCM status. From this information we will be able to implement a comparison scope which will only load the changed fragments, avoiding to load the complete UML model. It will lead to considerable cpu time and memory usage gains and will enable to handle the minimal set of model fragment during a comparison.
To do so we need to implement a first analysis pass to build the minimal scope of the comparison, and then leverage this scope during the whole comparison process.
In terms of memory gains, we expect to move from a memory scaling according to the number of fragments in the models to a memory scaling according to the number of changed fragments.
In terms of performance, the improvement will be of a comparable level of magnitude than for memory as the use of Logical Models will result in a drastic reduction of processing from the current situation (we compare the whole model) to the comparison of the minimal set of consistent UML fragments.
A new API will be provided to resolve the minimum set of fragments for a two way compare of two different versions of a UML model / Diagram e.g. left and right related diagram and model fragments in order to enable a compare session independently of the projects loaded in the work space.

Update the generic engine, UML engine and UI to avoid any un-necessary proxy resolution

Once the scope is defined the comparison engine (responsible for the match and diff process) and the user interface presenting the result should never ever resolve proxies which are out of this scope.

Performance tests

A performance evaluation and a profiling campaign will be done to illustrate these enhancements. This tests will cover models with characteristics similar to:

Small Nominal Large
Fragments 99 399 947
Packages 97 389 880
Classes 140 578 2169
Primitive Types 581 5370 17152
Data Types 599 5781 18637
State Machines 55 209 1311
States 202 765 10156
Dependencies 235 2522 8681
Transitions 798 3106 49805
Operations 1183 5903 46029

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